question_answer 4)

 What is the difference between a planet and a comet, as given in the story?  

Answer:

The difference between a planet and a comet is that the number of planets is fixed. But comets can be new which come from the remote comers of the solar system. Both orbits round the sun. But comet's orbits are highly eccentric. So once in a while a comet comes close to the sun it has a longish tail that is lit brilliantly by the sunlight and then it recedes into darkness, not to be seen again for years or for centuries.